An ultra-high-strength screw is known from European patent application No. EP 2 594 653 A1 corresponding to U.S. Pat. No. 9,145,910 B2.
A fastener manufacturing method is known from German patent No. DE 2 415 619 A1 corresponding to U.S. Pat. No. 4,037,281.
A method of manufacturing screws is described in document WORTH: “Manufacturing screws and nuts” (pages 1773-1776). The document describes the entire process of forming the shaft, rolling the thread and hardening and tempering the thread.
The article “Tempering (metallurgy)” from WIKIPEDIA describes the process of tempering.
The article “Induction hardening” from WIKIPEDIA describes the process of induction hardening.
A membrane reaction apparatus for recovering heat of reaction is known from German patent No. DE 600 16 369 T2 corresponding to U.S. Pat. No. 9,400,215 B2.